Plug-in expulsion fuse with seal between exhaust terminal and stationary contact sleeve

ABSTRACT

The exhaust terminal of an expulsion fuse is telescoped within a stationary contact sleeve with a seal therebetween to prevent flow of arc products between the terminal and the contact sleeve.

United States Patent Harold H. Fahnoe Evanston, Ill.

[21] Appl. No. 857,883

[22] Filed Sept. 15, 1969 [45] Patented Apr. 20, 1971 [73] Assignee S 8: C Electric Company Chicago, Ill.

[72] Inventor [54] PLUG-IN EXPULSION FUSE WITH SEAL BETWEEN EXHAUST TERMINAL AND STATIONARY CONTACT SLEEVE 5 Claims, 7 Drawing Figs.

[52] US. Cl 337/282 [5 1] Int. Cl e H01h 85/38 [50] Field ofSearch ZOO/149.1;

[56] References Cited UNITED STATES PATENTS 3,501,731 3/1970 Patterson 337/203 3,513,437 5/1967 McMorris 337/280 3,268,693 8/1968 Linton 337/201 x 2,184,760 12/1939 Wallace 200/1491 Primary Examiner-Bernard A. Gilheany Assistant ExaminerDewitt M. Morgan Attorney-Robert R. Lockwood ABSTRACT: The exhaust terminal of an expulsion fuse is telescoped within a stationary contact sleeve with a seal therebetween to prevent flow of are products between the terminal and the contact sleeve.

PATENTED APR 20 151i SHEET 2 OF 3 PATENTED APRZO I971 SHEET 3 OF 3 PLUG-IN EXPULSION FUSE WITII SEAL BETWEEN EXHAUST TERMINAL AND STATIONARY CONTACT SLEEVE This invention is an improvement over the construction disclosed in l-Iamer et al. US. Pat. No. 3,339,l 18, issued Aug. 29, 1967, and is particularly .adapted for use with the switchgear disclosed in Beebe application, Ser. No. 858,458, filed Sept. 16, I969.

When an expulsion fuse is mounted in a drawer, such as a drawer shown in the above Pat, it is desirableto support the fuse from one end in cantilever fashion with the free expulsion end arranged to discharge into an exhaust control device. Since the fuse is supported only at one end when it is withdrawn or the drawer is opened, it is undesirable to mount the exhaust control device on its exhaust end because of its weight.

' Among the objects of this invention are: To provide an expulsion fuse adapted to be supported at one end in a horizontally movable drawer with the other exhaust end adapted to be telescopically related to a stationary contact sleeve which forms a part of an exhaust control device; and to provide a seal between a cylindrical terminal at the exhaust end of the fuse and the contact sleeve to prevent flow of expulsion products therebetween. 7

According to this invention an expulsion fuse of the solid material type has a threaded stud extending eridwise from the fuse at one end for mounting on a horizontally movable drawer. At its other end the fuse has a cylindrical exhaust terminal that telescopes into a stationary cylindrical cont act sleeve which fonns a part of an exhaust control device. A pair of annular grooves is provided on the cylindrical exhaust terminal intermediate its ends in each of which a sealing ring is located that is formed of resilient material, such as tetrafluoroethylene or Teflon. The sealing rings prevent flow therepast of are products incident to blowing of the fuse thereby forcing the are products to flow through the sleeve. into the exhaust control device.

In the drawings:

FIG. 1 is a perspective view of a fuse drawer having a fuse constructed in accordance with this invention.

FIG. 2 is a plan view, partly in section and at an enlarged right to left,

FIG. 6 is a horizontal sectional view taken generally along line 6-6 of FIG. 3.

FIG. 7 is a view, in end elevation, of one of the covers or end plates for the housing of the exhaust control device.

In FIG. 1 the reference character 10 designates, generally a fuse drawer for use particularly in the switch gear described in the above application. Thefuse drawer 10 includes a metallic fuse panel ill from which upper and lower channel members .12 and i3 extend rearwardly to form a frame structure.

Vertical support plates 14 interconnect the channel members l2 and 13. Insulating barrier plates 15 are provided in parallel spaced relation with respect to expulsion fuses which are indicated, generally, at 16. For a three-phase system, three expulsion fuses 16 are employed. Also extending rearwardly from therear side of panel 11 are metallic brackets 17 from which insulators 18 project inwardly of the fuse drawer 10. Each of the insulators 18 has a metallic end cap 19.

Fuse terminal brackets 22 are mounted at the distal ends of the insulators 18 on the metallic end caps 19. Contact arms 23 extend laterally and inwardly from the fuse terminal brackets 22 to provide connections to switch blades which are arranged to connect the fuses 16 for energization into a loop circuit.

' Each of the expulsion fuses 16 includes a fuse tube 24 of insulating material having a cylindrical exhaust terminal 25 at its inner end for plug-in contact engagement with T-shaped exhaust control devices indicated, generally, at 26. The control devices 26 are mounted on metallic end caps 27 of stationary insulators 28 which are mounted on a rear panel of the switchgear (not shown).

In FIG. 4 the details of construction of one of the expulsion fuses 16 are shown. Within the fuse tube 24 there is an expulsion fuse assembly that is indicated, generally, at 31. It includes a terminal stud 32 which extends through the end of the exhaust terminal 24 and is secured in place by nuts 33. To the inner end of the terminal stud 32 a strain wire 34 and a fusible element 35 are connected. They are located in a metallic exhaust chamber 36. The other ends of the strain wire 34 and fusible element 35 are connected to one end of an arcing rod 37 which is movably mounted in a bore 38 in a lining 39 of arc extinguishing material, such as boric acid. Adjacent the exhaust chamber 36, the bore 38 opens into an enlarged bore section 40. At the opposite end of the arcing rod 37 there is a contact button 43 that is arranged to be engaged by contact fingers 44 of an arcing rod sleeve 45. A garter spring 46 acts to bias the distal ends of the contact fingers 44 into good contact engagement with the cylindrical surface of the contact button 43. The arcing rod sleeve 45 extends from an arcing rod sleeve stop 47. A metallic collar 48 surrounds the contact fingers 44 to prevent spreading thereof when relatively heavy short circuit current flows therethrough. The metallic arcing rod sleeve stop 47 is connected to one end of a conducting tube 49 which extends along the'inside of the fuse tube 24 to the left end whereit has a press fit with a knurled head 50 of an end plug 51. A threaded stud 52 extends laterally from the end plug 51.

As shown in FIG. 2 the threaded stud 52 is arranged to be screwed into the metallic end cap 19. When the fuse drawer 10 is withdrawn, the fuse 16 is supported in a cantilever fashion by the threaded stud 52. The entire weight of the fuse 16, including the weight of the cylindrical exhaust terminal 25, is then supported only by the stud S2. The overall length of the fuse 16 may be of the order of 18 inches. Thus it is desirable to have a minimum of weight at its distal end to be supported by the threaded stud 52, when the fuse drawer I0 is opened. In addition to supporting the fuse 16 the threaded stud 52 acts as a terminal to provide a connection to the fuse terminal bracket 22 from which the contact arms 23 extend. An end plug retainer ferrule 53 overlies the end of the fuse tube 24 and the end plug 5! to assist in holding the latter in position and to provide contact engagement with the fuse terminal bracket 22.

For 1 moving the arcing rod 37 through the bore 38 on blowing ofthe fusible element 35 and the strain wire 34, a coil compression spring 54 is provided. At its inner end it reacts against the arcing rod sleeve stop 47. At its outer end it reacts against a flange 55 on a spring insulator 56 which bears against a spring cap 57 to which one end of an arcing rod extension 58 is secured The outer end of the arcing rod extension 58 forms an integral part of the arcing rod 38. A filling of an epoxy resin 59 between the inner surface of the fuse tube 24 and the outer surface of the lining 39 of arc extinguishing material and the outer surface of the conducting tube 49 provide an integral construction.

When the fusible element 35 and strain wire 34 blow as a result of an overload or short circuit, an arc is formed between the remaining ends of the strain wire 34 and the fuse element 35 or between the terminal stud 32 and the retreating end of the arcing rod 37. Since the arcing rod 37 no longer is restrained, it moves through the enlarged bore section 30 into the bore 38 under the influence of the coil compression spring 54. The end plug 51 effectively closes off the adjacent end of the conducting tube 49. The products incident to the are thus drawn and incident to evolution of. gas from the arc extinguishing material 39 are required to flow outwardly through the metallic exhaust chamber 36 and to flow through arcuate exhaust openings 60, FIG. 5, in the outer end of the cylindrical exhaust terminal 25. Here it will be observed that the exhaust openings 60 are provided on opposite sides of a to telescope within a cylindrical interior surface 64 of an adapter or contact sleeve 65 which opens into the. control device 26. The adapter or contact sleeve 65 extends through a suitable opening in a wall 66 of an elongated tubular metallic housing 67 which forms a part of the control device 26. The adapter or contact sleeve 65 and the elongated metallic housing 67 provide a generally T-shaped configuration. Annular grooves 68 are formed in the reduced diameter end section 63 of the exhaust terminal 25 for receiving sealing.

rings 69 which are formed of a material having a relatively low coefficient of friction. For example they may be formed of tetraflurorethylene of which Teflon is an example. The sealing rings 69 are large enough in cross section to snugly engage the cylindrical interior surface 64 of the adapter or contact sleeve 65 and thus they prevent flow therepast of the are products which are discharged through the exhaust openings 60 into the tubular metallic housing 67.

In order to provide a good electrical connection between the exhaust terminal 25 and the adapter or contact sleeve 65 a contact sleeve extension 70 of a good conducting material, such as copper alloy, overlies the adapter or contact sleeve 65 and has contact fingers 71 which are urged by garter springs 72 into good contact engagement with a cylindrical contact section 73 of the exhaust terminal 25. A clamp nut 74, threaded on the adapter or contact sleeve 65, holds the contact sleeve extension 70 in good contact engagement therewith.

FIGS. 3 and 6 show the details of construction of the exhaust control device 26. It will be noted that an exhaust product deflector 75 is located in the wall 66 of the tubular metallic housing 67 in alignment with the opening through the adapter or contact sleeve 65 so that the are products flowing through the exhaust openings 60 in the exhaust tenninal 25 directly impinge thereon. The exhaust product deflector 75 may be formed of a copper alloy and it has a cylindrical base portion 76 which extends through a suitable opening in the wall 66 of the metallic housing 67 and is suitably secured thereto. Extending inwardly from the base portion 76 is an integral conical section 77 which has an apex angle of 90. As a result the high velocity flow of are products from the fuse 16 is redirected principally toward the opposite ends of the housing 67. Since the reactions due to the high velocity flow of are products are equal and opposite, they tend to neutralize and to confine the resultant forces to tension of the walls 66 of the housing 67 which are of ample strength to resist such forces. Exhaust product cooling and condensing means, indicated generally at 78, are provided at the ends of the housing 67. They include helical coils 79 of heavy wire mesh which are wound around metallic studs 80 and between washers 81 at the inner ends of the studs 80 and covers or metallic end plates 82 at the outer ends. The covers or end plates 82 are located in grooves 83 near the ends of the housing 67 and the edges 84 thereof are turned over to hold the covers or end plates 82 in place. In FIG. 7 one of the covers or end plates 82 is shown. It is provided with a number of exhaust openings 85 which relieve the pressure that is generated within the housing 67 on blowing of the fuse 16.

In order to provide a rugged support for the exhaust control device 26 on the insulator 28, support means, indicated generally at 87 is employed. It comprises a channel-shaped cradle 88 as shown in FIG. 3 The cradle 88 is located in overlying relation and symmetrically with respect to the exhaust product deflector 75. Its ends 89 overlie ears 90 that are welded or otherwise secured to the outer surface of the wall 66 of the housing 67. Bolts 91 interconnect the ends 89 of the channel-shaped cradle 88 and the ears 90. Flat head screws 92 extend through'the bottom of the cliannel-shaped cradle 88 into the metallic end cap 27 on the insulator 28 to hold the assembly including the control device 26 securely in place. Also this provides an electrical connection to the inner or distal end of the fuse 16 which is completed, for example, by a conductor rod extending through the insulator 28 and projecting rearwardly thereof for connection to a suitable load conductor.

As pointed out, the fuse 16 has a plug-in connection with the exhaust control device 26. The dimensions of the annular grooves 68 in the exhaust terminal 25 are related to the dimensions of the O-rings or sealing rings 69 therein and to the diameter of the interior surface 64 of the adapter or contact sleeve 65 so that the fuse 16 can be readily inserted in or removed from the exhaust control device 16 upon lengthwise movement incident to opening and closing of the fuse drawer 10. In the fully inserted position the sealing rings 69 prevent gas or vapor leakage therepast during the operation of the fuse 16.

Because of the relatively lightweight of the fuse l6 and the lower mechanical reaction forces of the fuse 16 incident to its operation combined with the exhaust control device 26, the

supporting structure for the fuse l6 and its insulator 18 can be relatively light in weight and construction thereby making an economical and compact drawout type of fuse drawer 10 or fuse carrier suitable for use in very compact metal enclosed fuse-gear or fused-switchgear.

The construction of the fuse 16 described herein is suitable for application on electric power systems operating at voltages up to l 5 kv. and where short circuit duties are expected of the order of 20,000 amperes. The fuse 16 is designed to have a continuous current carrying capability of up to 200 amperes. The same general construction can be employed with somewhat larger dimensions for use with higher operating voltages and/or higher current carrying capabilities.

The enlarged ,bore section 40 in the lining 39 of are extinguishing material is preferably employed in connection with arcing rods 37 of relatively small diameter for use in fuses having a continuous current carrying capacity less than 200 amperes. This permits the arc incident to the blowing of the fusible element 35 and strain wire 34 to expand and not produce excessive gas or vapors during the initial travel of the arcing rod 37 into the bore 38 and while it is moving relatively slowly from its position as shown in FIG. 4 to one within the enlarged bore section 40 where current interruption actually takes place. For the larger continuous current carrying fuses, larger sizes of arcing rods 37 are employed and the enlarged bore section 40 is not provided. Rather the bore 38 at the same diameter extends fully to the right end of the lining 39 of arc extinguishing material. For such fuses, since the melting time for the fuse element 35 is relatively long an appreciable amount of time in the first half cycle of fault current is required to melt it. Accordingly, maximum exposure of the resulting arc to the surface of the bore 38 is required in order to effect interruption at the first normal current zero.

For the smaller sizes of the arcing rod 37 the contact button 43 is lengthened so that it remains in contact engagement with the contact fingers 44 for a longer time so that the time required for separation is increased. This also provides some additional frictional resistance to endwise movement of the arcing rod 37 and reduces the violence of operation or internal pressures in the fuse 16 by slowing initially the rate at which the arcing rod 37 is withdrawn by the spring 54 and the arc is extended within the lining 39 of are extinguishing material.

lclaim:

1. An expulsion fuse for mounting on support means on which a cylindrical contact sleeve is mounted comprising:

a fuse tube,

a mounting terminal at one end of said fuse tube,

an externally grooved cylindrical exhaust terminal at the other end of said fuse tube for slidably telescopically i an expulsion fuse assembly engaging said contact sleeve to have plug in contact engagementtherewith,

which a cylindrical contact sleeve is mounted comprising:

a fuse tube,

a mounting terminal at one end of said fuse tube,

outwardly endwise extending support means on said mounting terminal for mounting said expulsion fuse in cantilever fashion for endwise movement intoand out of said cylindrical contact sleeve,

a cylindrical exhaust terminal at the other end of said fuse tube for slidably telescopically engaging said contact sleeve to have plug in contact engagement therewith,

an expulsion fuse assembly within said fuse tube interconnecting said terminals, and sealing means on said cylindrical exhaust terminal to prevent flow between it.

and said contact sleeve of products incident to operation of said expulsion fuse assembly.

within said fuse tube' i 3. An expulsion for mounting on support means on which a cylindrical contact sleeve is mounted comprising: a fuse tube, Y a mounting terminal at one end of said fuse tube,

a cylindrical exhaust terminal at the other end of said fuse tube for telescopically engaging said contact sleeve and having a pair of annular grooves in spaced relation intermediate its ends,

an expulsion fuse assembly within said fuse tube interconnecting said terminals, and

a resilient ring in each. of said grooves of a material having a relatively low coefficient of friction to provide a seal between said cylindrical contact sleeve and said cylindrical exhaust terminal to prevent flow therebetween of products incident to operation of said expulsion fuse assembly.

4. The expulsion fuse according to claim 3 wherein said mounting tenninal includes outwardly endwise extending support means for mounting said expulsion fuse in cantilever fashion and independently of said'contactsleeve-for endwise movement into and out of the same.

5. The expulsion fuse according to claim 4 wherein said endwise extending support means comprises a threaded stud. 

1. An expulsion fuse for mounting on support means on which a cylindrical contact sleeve is mounted comprising: a fuse tube, a mounting terminal at one end of said fuse tube, an externally grooved cylindrical exhaust terminal at the other end of said fuse tube for slidably telescopically engaging said contact sleeve to have plug in contact engagement therewith, an expulsion fuse assembly within said fuse tube interconnecting said terminals, and a resilient ring of a material having a relatively low coefficient of friction in the groove of said cylindrical exhaust terminal to prevent flow between it and said contact sleeve of products incident to operation of said expulsion fuse assembly.
 2. An expulsion fuse for mounting on support means on which a cylindrical contact sleeve is mounted comprising: a fuse tube, a mounting terminal at one end of said fuse tube, outwardly endwise extending support means on said mounting terminal for mounting said expulsion fuse in cantilever fashion for endwise movement into and out of said cylindrical contact sleeve, a cylindrical exhaust terminal at the other end of said fuse tube for slidably telescopically engaging said contact sleeve to have plug in contact engagement therewith, an expulsion fuse assembly within said fuse tube interconnecting said terminals, and sealing means on said cylindrical exhaust terminal to prevent flow between it and said contact sleeve of products incident to operation of said expulsion fuse assembly.
 3. An expulsion for mounting on support means on which a cylindrical contact sleeve is mounted comprising: a fuse tube, a mounting terminal at one end of said fuse tube, a cylindrical exhaust terminal at the other end of said fuse tube for telescopically engaging said contact sleeve and having a pair of annular grooves in spaced relation intermediate its ends, an expulsion fuse assembly within said fuse tube interconnecting said terminals, and a resilient ring in each of said grooves of a material having a relatively low coefficient of friction to provide a seal between said cylindrical contact sleeve and said cylindrical exhaust terminal to prevent flow therebetween of products incident to operation of said expulsion fuse assembly.
 4. The expulsion fuse according to claim 3 wherein said mounting terminal includes outwardly endwise extending support means for mounting said expulsion fuse in cantilever fashion and independently of said contact sleeve for endwise movement into and out of the same.
 5. The expulsion fuse according to claim 4 wherein said endwise extending support means comprises a threaded stud. 